Bumpers and bumper reinforcements on modern vehicle may be formed from polymer materials, such as glass-filled polymers. Such materials may crack under impact loading, due to collision forces operating on the bumper, for example. Propagation of a bumper reinforcement crack may cause a portion of the bumper reinforcement to separate from the remainder of the bumper reinforcement. If the bumper reinforcement is enclosed within a shell or cover, the user may not be able to visually detect the damaged condition of the bumper reinforcement.